Wastewater separator and method of using same

ABSTRACT

A method for pretreating a wastewater stream containing grease and food particles before the stream enters a sewer includes the steps of directing said wastewater stream to a separation area; directing said wastewater stream along a preferred flow path within said separation area, said preferred flow path being sized and shaped to permit said grease to rise out of said wastewater stream; trapping said grease which rises out of said wastewater stream; extending a wastewater outlet substantially across said separation area; accelerating said remaining wastewater, carrying said food particles, through said outlet from said separation area, thereby sucking said food particles away from said separation area; and directing said wastewater and said food particles toward said sewer system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 09/732,299,filed Dec. 8, 2000, now U.S. Pat. No. 7,011,752, which claims thebenefit of Canadian Application No. CA 2,299,134, filed Feb. 23, 2000,the contents of all of which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to the field of wastewater management, and, inparticular, to devices known as grease traps, which are used forseparating grease and oil from wastewater before permitting thewastewater to enter into a sanitary or storm sewer systems.

BACKGROUND OF THE INVENTION

Some commercial establishments, such as restaurants, produce aconsiderable amount of waste or drainage water which often contains highlevels of grease or oil. Such contaminants can adversely affect thesewage treatment plants and can clog up the sewers. Therefore, mostjurisdictions require that such grease and oil be removed from thewastewater at the commercial establishment before it is permitted toenter the sewage system. To effect such removal, a restaurant willtypically provide a grease trap on its wastewater outlet line.Essentially, wastewater passes into the grease trap at one end andwithin the grease trap, the grease which has a lower specific gravitythan water rises and forms a layer on top of the grease trap. A fluidoutlet from the grease trap is positioned below the level of the greaselayer to permit substantially grease free wastewater to be removed. Inthis way, the grease is collected in the grease trap and it may beperiodically removed by direct bailing the grease out of the top of thegrease trap. The grease is then disposed of as solid waste, for example,at landfill sites.

One problem with conventional grease traps is that particles of food arealso present in the wastewater stream, such as bits of lettuce, meat andother waste solids. These solid waste particles have two significanteffects. First, they significantly increase the volume of the wastelayer collected. As a result, the grease trap becomes filled quickly andthe collected waste must be removed frequently. Second, the bits ofsolid matter caught in the grease trap tend to decompose, anaerobically,which creates noxious gases, making the job of manually bailing thegrease from the grease trap extremely unpleasant. Thus the prior artdevices suffer from being both labour intensive (i.e. they fill quicklyand require more frequent cleaning) and extremely unpleasant tomaintain.

A number of devices for separating waste from wastewater are alreadyknown. U.S. Pat. No. 1,407,936 discloses an apparatus and method forseparating matter from effluents. The apparatus includes a containerwhich is wide at its inlet end and narrow at its outlet end. Theeffluent enters the container through an inlet pipe at the bottom of thecontainer, and the effluent stream is directed upward. At that point,solid particles settle on the floor of the container, and can be removedmanually through a separate valve created for that purpose. Meanwhile,the effluent stream continues through the container, and the floatingwaste separates from the water stream, which is directed to the outletpipe at the opposite end of the container.

This device separates solid waste from the floating waste, such asgrease, and takes the solid waste out of the effluent stream. However,the container must be manually emptied of solid waste separately fromthe removal of the grease. This is a time-consuming activity, and itmust be done fairly frequently to prevent clogging of the inlet pipe.

U.S. Pat. Nos. 2,138,985, 3,849,311 and 4,372,854, for example, alsodisclose devices for separating light waste, such as oil or grease, fromwater. However, the devices in these patents all suffer from the problemthat solid waste is trapped in the trap.

SUMMARY OF THE INVENTION

Therefore, what is desired is a device for effectively separating lightwaste, such as oil or grease from water. For the purpose of thisinvention it shall be understood that the term “light waste” shall referto waste having a specific gravity slightly less than water and whichtherefore tends to rise when submerged in water. Also the term “heavywaste” shall be used to refer to waste which has a specific gravitywhich is greater than water, and which therefore tends to sink whenplaced in water. The desired device according to the present inventionshould also preferably function so as to prevent solid or heavy waste inthe wastewater stream from being trapped in the layer of grease.Finally, the device preferably should not have to be frequently manuallyemptied of both solid waste and of grease.

Accordingly, in one aspect, the present invention is directed to awastewater separator to separate waste from a mixed wastewater streambefore the mixed wastewater stream is directed into a sewer system, themixed wastewater stream including one or more of heavy waste, lightwaste and water. The wastewater separator comprises a separationcontainer, a wastewater inlet to the separation container and awastewater outlet from said separation container. The separationcontainer comprises (1) a wastewater stream director within theseparation container, the wastewater stream director being sized, shapedand positioned relative to the wastewater inlet to direct the wastewaterstream along a preferred flow path to permit the light waste to separatefrom the wastewater stream in a first direction to a collection area andto permit the heavy waste to separate from the wastewater stream in asecond direction towards a heavy waste removal area; and (2) aflow-directing outlet baffle within the separation container fordirecting the wastewater stream to the wastewater outlet from the heavywaste removal area to remove the heavy waste from the separationcontainer.

Also, the wastewater separator preferably further comprises a coverdetachably attachable to the container, the cover being sized and shapedto removably cover an opening on the top of the container.

The wastewater separator still further preferably comprises airentraining means associated with the wastewater inlet for entraining airinto the wastewater stream.

In another aspect, the invention is directed to a wastewater separatorto separate light waste from a mixed wastewater stream. The wastewaterseparator comprises a separation container having an inlet end and anoutlet end, a wastewater inlet to the separation container, a wastewateroutlet from the separation container, and air entraining meansassociated with the wastewater inlet to entrain air into the wastewaterstream. The separation container comprises a wastewater stream directorin the container sized, shaped and positioned to direct the wastewaterstream along a preferred flow path which is generally diagonal acrossthe container to facilitate separation of the light waste. Theseparation container further comprises a flow-directing outlet baffle inthe container for directing said wastewater stream from a downstream endof the preferred flow path to the wastewater outlet.

In a further aspect the present invention provides a wastewaterseparator to separate light waste from a mixed wastewater stream, saidwastewater separator comprising:

a separation container having an inlet end and an outlet end;

a wastewater inlet to said separation container;

a wastewater outlet from said separation container; and

air entraining means associated with said wastewater inlet to entrainair into said wastewater stream;

said separation container comprising:

a wastewater stream director in the container, said wastewater streamdirector being sized, shaped and positioned to direct the wastewaterstream along a preferred flow path which is generally diagonal acrosssaid container to facilitate separation of said light waste; and

a flow-directing outlet baffle in said container for directing saidwastewater stream from a downstream end of said preferred flow path tosaid wastewater outlet.

In a further aspect the present invention provides a method ofpretreatment of a wastewater stream before said stream enters a sewer,where said wastewater stream contains grease and food particles, saidmethod comprising the steps of:

1) directing said wastewater stream to a separation area;

2) directing said wastewater stream along a preferred flow path withinsaid separation area, said preferred flow path being sized and shaped topermit said grease to rise out of said wastewater stream;

3) trapping said grease which rises out of said wastewater stream; and

4) directing said remaining wastewater, carrying said food particles,out of said separation area and toward said sewer system.

In a further aspect the present invention provides a method ofpreventing grease or oil from being carried out in wastewater from afood preparation establishment to a sewer system, said method comprisingthe steps of:

1) entraining air into said wastewater stream;

2) directing said wastewater stream to a separation area; then

3) directing said wastewater stream along a preferred flow path withinsaid separation area, said preferred flow path being sized and shaped topermit said grease to rise out of said wastewater stream; then

4) permitting said grease to rise out of said wastewater stream;

5) containing said grease within said separation area;

6) directing said wastewater stream, carrying said food particles, outof said separation area and toward said sewer system.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made, by way of example only, to the drawings ofthe present invention which illustrate the preferred embodiment, and inwhich:

FIG. 1 is a cross-sectional elevation view of the wastewater separator;

FIG. 2 is a top view of the wastewater separator; and

FIG. 3 shows the quarter-turn fastener described herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, the wastewater separator is generallydesignated by reference numeral 10. The wastewater separator 10 is forseparating waste from a mixed wastewater stream before the disposal intoa sewer system, where the mixed wastewater stream includes heavy waste,light waste and water. “Heavy waste” includes bits of solid food and anyother waste with a density greater than that of water. Similarly, “lightwaste” is any waste in the mixed wastewater stream which has a densityless than that of water, such as, for example, grease and oil. It willfurther be appreciated that the present invention is directed to aself-contained device which is used on an inlet to a sewer system from acommercial or industrial premises involved, typically, in food servicepreparation.

The wastewater separator 10 comprises a wastewater inlet 12, awastewater outlet 14 and a separation container 22. The separationcontainer 22 is filled with water which is the medium typically used totransport and dispose of various liquid and solid wastes and which formthe bulk of the mixed wastewater stream. The mixed wastewater stream isadmitted to the separation container 22 through the wastewater inlet 12,and exits from the separation container 22 through the wastewater outlet14. As will be more particularly described below, the light waste isseparated from the wastewater stream in the separation container 22, andtrapped there in what is referred to as a collection area. Thewastewater stream exits the separation container 22 through thewastewater outlet 14, carrying the heavy waste. As will be appreciatedfrom the explanation which follows, the separation of the mixedwastewater stream into a collected light waste and removed heavy wasteis accomplished in part by directing the wastewater stream along apreferred flow path through the separation container 22.

The wastewater inlet 12 is sized and shaped to be in water-tightcommunication with a wastewater pipe carrying the wastewater stream tothe wastewater separator. Similarly, the wastewater outlet 14 is sizedand shaped to be in water-tight communication with a further wastewaterpipe which carries the wastewater stream away from the wastewaterseparator 10 and into a sewer.

Preferably, to achieve this water-tight communication, the wastewaterinlet 12 and the wastewater outlet 14 include an inlet adaptor 18 andoutlet adaptor 20, respectively, which adaptors facilitate the plumbingconnection between each of the wastewater inlet 12 and outlet 14, andthe wastewater pipes (not shown) which carry the wastewater stream. Inthe preferred embodiment, the inlet adaptor 18 and the outlet adaptor 20are straight connections (as opposed to, say, 90° elbow connectors).However, the inlet and outlet adaptors 18 and 20 may be any shape and/orsize that is necessary to achieve the water-tight connection with thewastewater pipes carrying the wastewater stream to and from thewastewater separator 10.

It will be appreciated by those skilled in the art that the wastewaterinlet and outlet 12 and 14 need not include adaptors 18 and 20. Rather,any configuration is sufficient if it allows the wastewater stream totravel from the wastewater pipe through the wastewater inlet 12, andthrough the wastewater outlet 14 to the other wastewater pipe. So, forexample, the inlet 12 and outlet 14 may simply be pipe sections, withoutadaptors, that are sized and shaped to be inserted directly into thewastewater pipes by pressure fit. Of course it will be appreciated bythose skilled in the art that any such plumbing connection must be madein accordance with local building and safety codes. What is important isthat the inlet and outlet configurations allow the wastewater stream totravel from the wastewater pipe through the wastewater inlet 12, andthrough the wastewater outlet 14 to the next downstream wastewater pipefor delivery to a sewer system.

In the preferred embodiment, the separation container 22 is rectangularin both vertical and horizontal cross section. Thus, the container 22includes a substantially rectangular container floor 24, and foursubstantially rectangular walls 26, 28, 30 and 32 extending generallyorthogonally upwardly from the edges of container floor 24 such that aclosed container 22 is formed. The walls 26, 28, 30 and 32 are all ofthe same height. The wastewater inlet 12 extends through the upperportion of inlet wall 26 and the wastewater outlet 14 extends throughthe upper portion of outlet wall 28. This form is preferred because itcan be molded from plastic, for example, by injection molding. Further,conventional grease traps tend to be rectangular and thus by making theinstant invention rectangular as well, it can be fit into the existingspace for a conventional trap as a retrofit.

The preferred size range for the container is between 10 and 20 gallons,with 12 gallons being the optimum size. This size is the volume of thecontainer, and this volume has proved adequate for a waste stream ratedat 20 gpm. It will be appreciated that the device should be large enoughthat it does not have to be emptied too frequently, but small enough tofit comfortably into interior building space in the back of a kitchen,storage area or the like.

It will be appreciated by those skilled in the art that a rectangularshape for the container 22 is preferred. The wastewater separator 10will typically be located under flat floors and/or against flat walls,and the wastewater pipes will typically run parallel to those wallsand/or pipes. As such, is preferred to have a container 22 whosedimensions are similarly flat so as to allow the wastewater separator 10to fit more easily into its required location. However, as stated above,the container 22 may be any shape that allows it to hold water, andallows for the separation of light waste from the wastewater stream,without departing from the scope of the invention.

The separation container 22 further comprises a wastewater streamdirector within the container 22, and most preferably releasably coupledthereto in a manner hereafter described. The wastewater stream directoris sized, shaped and positioned relative to the wastewater inlet todirect the wastewater stream along a preferred flow path within thecontainer 22. In the preferred embodiment, the wastewater streamdirector comprises a flow-directing inlet baffle 34 attached to the wall26 over the inlet 12 for directing the wastewater stream passing throughthe inlet 12 downward to the bottom of the container 22. Also providedis a separation flow director in the form of a ramp 36 immediatelydownstream of the baffle 34. In the most preferred form the ramp 36 isattached to, by being formed in, the container floor 24.

It will be appreciated that the wastewater stream director need not besolely in the form of the flow-directing inlet baffle 34 and the ramp36. For example, other configurations of elements could be used toaccomplish the same function, such as using the flow-directing inletbaffle 34 as the wastewater stream director. What is desired is todirect the wastewater stream along the preferred flow path, and anystructure that does so can serve as the wastewater stream director.

The wastewater separator 10 further comprises a heavy waste removal area42 which, in the preferred embodiment, comprises the portion of thebottom of the container 22 which is immediately downstream from theupper edge 38 of ramp 36.

The separation container 22 further comprises a flow-directing outletbaffle 44, in the container 22, and most preferably removably coupledthereto, for directing the wastewater stream from the heavy wasteremoval area 42 in the container 22 to the wastewater outlet 14. Theoutlet baffle inlet 48 (i.e. the inlet of the flow-directing outletbaffle 44), is preferably adjacent to and downstream from the heavywaste removal area 42, on the floor 24. It is preferable to position theoutlet baffle inlet 48 as low as possible in the container 22 so as toensure that light waste is not drawn into the outlet baffle 44 and outthrough the wastewater outlet 14.

The separation of the mixed wastewater stream by the present inventioncan now be understood. As the wastewater stream enters through thewastewater inlet 12, it contacts the flow-directing inlet baffle 34,which is sized, shaped and positioned to direct the wastewater streamdownward to the bottom of the container 22. The upper portion of theflow-directing inlet baffle 34 acts as a mixing section which convertsthe wastewater stream to a substantially isotropic fluid. As such, airbubbles introduced at this point are permitted to adhere to the smallgrease droplets which have an affinity for each other. Also, theflow-directing inlet baffle 34 is sized and shaped so that, as the waterstrikes the inlet baffle 34 and tumbles downward, the flow of thewastewater stream becomes turbulent and air bubbles introduced at a flowcontrol orifice are mixed into the wastewater stream. Thus, in thepreferred embodiment, the flow-directing inlet baffle 34 also acts as anair entraining means, associated with the wastewater inlet 12, forentraining air into the mixed wastewater stream.

The mixed wastewater stream exits from the flow-directing inlet baffle34 and flows along the ramp 36. Good results have been obtained with aramp having a radiused top as shown. The combination of theflow-directing inlet baffle 34 and the ramp 36 functions to direct thewastewater stream along a preferred flow path within the container 22.As more particularly described below, the preferred flow path permitsthe light waste to separate from the wastewater stream in a firstdirection to a collection area and permits the heavy waste to separatefrom the wastewater stream in a second direction towards the heavy wasteremoval area 42.

The preferred flow path is indicated in FIG. 1 by the dotted line, andhas a first section in the container 22, as well as a second section.The first section extends upward from the downstream end of theflow-directing inlet baffle 34 and away from the wastewater inlet 12.The separation of the light waste from the wastewater stream takes placein the first section. Because the light waste is of higher buoyancy thanwater, the light waste will rise to the collection area at the surface60 of the water contained in the container 22. Preferably the firstsection of the preferred flow path will extend diagonally from thebottom of the inlet end of the container 22. Such a flow path maximizesand optimizes the flow path length and hence the time for buoyancyseparation of light waste, thus enhancing the amount of separation oflight waste. Also, the air bubbles that are entrained into thewastewater stream by the flow-directing inlet baffle 34 will enhance theseparation of the light waste from the wastewater stream. Thisenhancement results from the greater buoyancy of the air bubbles, whichwill also tend to rise to the surface of the water, and which will thusexert a force upon the light waste in the form of grease droplets (forwhich the air bubbles have an affinity as noted above) and propel it tothe surface.

It will be appreciated by those skilled in the art that the airentraining means can take other forms than the inlet baffle 34. Forexample, the air entraining means could be a separate device or machinewhich actively and mechanically inserts bubbles into the wastewaterstream. What is important is that the air entraining means mixes airinto the wastewater stream before the separation stage, so that airbubbles will be present to assist in the separation of light waste.

As the wastewater stream exits the flow-directing inlet baffle 34, theheavy waste is carried up the ramp 36 and past the upper edge 38 by theforce of the current in the wastewater. At this point, the heavy wastewill fall from upper edge of the ramp into the heavy waste removal area42. The radius of the top edge is useful because it discouragesturbulent flow of the liquid passing over the ramp. Turbulent flow isundesirable because it can both carry heavy waste past the heavy wasteremoval area and erode trapped grease from the surface, if it reachesthat area. The present invention contemplates increasing thecross-sectional area and thus slowing the inlet flow stream to reducethe likelihood of turbulent flow in the separation area. This slowerflow carries the heavy waste up, over and then down the far side of theramp into the waste removal area. A more acute top edge 38 could lead toundesirable turbulence. Thus the ramp is preferably configured toencourage, as much as possible, over the design flow rates for thespecific application, laminar flow up and over the ramp and then throughthe outlet.

The path of the heavy waste is shown by solid arrows in FIG. 1.Preferably, the flow-directing inlet baffle 34 has an outlet area whichis sized and shaped to slow the wastewater stream sufficiently to permitthe heavy waste to settle downward as it is gently carried along by theslow current. As can now be appreciated, as the mixed wastewater streamis slowed, the heavy waste has more time to fall, under the influence ofgravity and the relative buoyancy effects, towards the bottom of thecontainer 22. Thus, most preferably, as the heavy waste reaches theupper edge 38 of the ramp 36 it will generally be at the bottom of thecontainer 22 and most likely in contact with the ramp 36. Similarly, theseparation of light waste is facilitated, as the light waste has moretime to separate from the wastewater stream due to a slower flow.

When the wastewater stream reaches the surface 60 of the water near theoutlet side of the container 22, it turns and enters the second sectionof the preferred flow path. The second section of the preferred flowpath extends downward from the downstream end of the first section, andcurves back toward the outlet baffle inlet 48, because the only exitfrom the container 22 is through the flow-directing outlet baffle 44 tothe wastewater outlet 14. As the outlet baffle inlet 48 is adjacent tothe heavy waste removal area 42, the wastewater stream travels throughthe heavy waste removal area 42 to enter the outlet baffle inlet 48,which acts as a heavy waste collector. The outlet baffle inlet 48 issized, shaped and positioned to remove heavy waste falling from thewastewater stream from the heavy waste removal area 42 as the wastewaterstream is directed out of the container 22. As it does so, it picks upthe heavy waste in the heavy waste removal area 42 and carries itthrough the flow-directing outlet baffle 44 to the wastewater outlet 14.

It will be appreciated by those skilled in the art that the outletbaffle inlet 48 need not be directly adjacent to the heavy waste removalarea 42, nor is it necessary for the preferred flow path to extenddirectly through the heavy waste removal area 42. However the simplestand most preferred form of the invention allows for the suction createdby the wastewater stream entering the outlet baffle inlet 48 to suck theheavy waste into the outlet baffle inlet 48. Less preferred but stillfeasible is to use mechanical means to push the heavy waste to theoutlet baffle inlet 48. This is less preferred because it would be moreexpensive, more difficult to use and more likely to fail. What isimportant is that the preferred flow path should have a combinedtrajectory and flow rate that permits the heavy waste in the mixedwastewater stream to be directed to the heavy waste removal area 42.

It will also be appreciated by those skilled in the art that thepreferred flow path need not be the precise flow path shown in FIG. 1.Rather any number of flow paths through the container 22 may act as thepreferred flow path. What is important is that the preferred flow pathbe sized and shaped to permit the light waste to separate from thewastewater stream in a first direction to a collection area and topermit the heavy waste to separate from the wastewater stream in asecond direction towards the heavy waste removal area 42.

The light waste that has been separated and has floated to the surface60 of the water in the container 22 will need to be periodicallyemptied. Accordingly, the wastewater separator 10 will preferablycomprise a cover 52, detachably attachable to the container 22. A gasket53 is also provided to make a good seal between the cover 52 and thecontainer 22. Most preferably, the cover 52 will include fourquarter-turn fasteners 54 at each corner of the cover 52. “Quarter-turnfastener” refers to a fastener which is sized and shaped to grip thecover 52 to the container 22 when in its closed position. However, thefastener can be moved to an open position by swivelling it approximately90°, or a quarter turn. In the open position, the cover 52 and container22 are not held together. As shown in FIG. 3, the quarter-turn fasteners54 preferably have a convenient finger grip portion 56, allowing easymanipulation for quickly fastening or unfastening the cover 52.Quarter-turn fasteners are preferable because they effectively andstrongly secure the cover 52 to the container 22, while still allowingthe cover 52 to be quickly detached. However, it will be appreciated bythose skilled in the art that quarter-turn fasteners are notspecifically required for the invention. For example, the cover 52 maybe detachably attachable by any suitable means, such as, for example,magnets attached to the cover 52 and container 22. It will also beappreciated that, though it is preferable for the cover 52 to bedetachably attachable to the container 22, the cover 52 may be morepermanently attached, such as, for example, by screws. This, however, isnot preferred, since the process of emptying the wastewater separator 10would be much more time consuming. Similarly, the cover 52 need not beattached at all (i.e. it may just rest on the container 22), though thisis not preferable either, for the cover 52 may get jolted aside, andwastewater may then leak or spill from the top of the container 22.

Every so often, the entire wastewater separator 10 will need to becleaned (as opposed to merely emptying the light waste). This cleaningwould include wiping down and scouring all of the surfaces inside thecontainer 22. To facilitate such cleaning, it is preferable that theflow-directing inlet baffle 34 and the flow-directing outlet baffle 44be detachably attached to the container 22. In this way the baffles 34and 44 themselves, as well as the surfaces of the container 22 behindthe baffles 34 and 44, can be easily cleaned.

Most preferably, the baffles 34 and 44 will be sized and shaped so as tobe slidably insertable into tracks mounted on the walls 26 and 28. Thetracks secure the baffles 34 and 44 to the container 22, while allowingthem to be easily withdrawn for cleaning. This withdrawal would be mostpreferably facilitated by a pair of inlet handles 55 on theflow-directing inlet baffle 34, and a pair of outlet handles 57 on theflow-directing outlet baffle 44. While a pair of handles on each baffleis most preferable for balancing ease of manipulation with ease ofmanufacture, it will be appreciated that one handle on each baffle canserve the same function. Similarly, three or more handles can also beincluded in order to provide a variety of possible grip points for aperson withdrawing the baffles.

It will be appreciated that other means may be used to make the bafflesdetachably attachable to the container 22. For example, the baffles andthe container 22 may both contain complementary snap fittings whichallow the baffles to be snap-fitted onto the container 22. What isimportant is that the baffles be easily detachable from the container22, yet be attached strongly enough attached so as not to detach duringthe operation of the wastewater separator 10. In the preferredembodiment, the baffles are held in position by securing the cover inplace.

Referring now to FIG. 2, it can be seen that in the preferredembodiment, inlet baffle inlet 62 corresponds in size to the wastewaterinlet 12, which in turn corresponds in size to the wastewater pipe thatcarries the wastewater stream to the wastewater separator 10. As theinlet baffle 34 extends downward, it widens, so that at the inlet baffleoutlet 40 the inlet baffle 34 extends substantially across thecontainer, from wall 30 to wall 32. This configuration is preferablebecause it allows the entire width of the container 22 to be used forthe process of waste separation. As the entire width of the container isin use for separation, the ramp 36 and the outlet baffle inlet 48 alsoextend substantially across the width of the container 22. The outletbaffle 44 is wide at the outlet baffle inlet 48, but small in height,compared to the outlet of the inlet baffle. This has the effect ofaccelerating the flow through the inlet of the outlet baffle. Thisencourages the heavy waste to be sucked away. The outlet baffle thenchanges shape as it extends upward to the wastewater outlet 14, in orderto correspond in size and shape with the other wastewater pipe carryingthe wastewater away from the wastewater separator 10. Also shown is anair relief valve 44 on the outlet baffle 48, which prevents suction frombeing able to establish a flushing action in the event of a sudden flow.Such a flushing action could cause the trap to completely empty, whichis undesirable.

As discussed above, the flow-directing inlet baffle 34 is preferablysized and shaped to slow the wastewater stream as it leaves the inletbaffle 34. This is achieved by selecting the cross-sectional area of theinlet baffle 34 to be such that the flow speed of the liquid is reducedas it leaves the inlet baffle 34. Thus, the inlet baffle 34 is wide atits outlet end and of sufficient height such that the cross-sectionalarea produces slow, smooth preferably laminar flow out of the outlet 40.The actual size of the outlet will vary depending upon the flow rate,which will also vary with the application. Reasonable results have beenachieved with an outlet cross-sectional area of between 10 and 13 squareinches with about 11.6 square inches being the most preferred for atypical use of 20 gpm.

It can now be appreciated that the present invention separates the lightwaste from the heavy waste in a mixed wastewater stream and directs thelight waste to a collection area while directing the heavy waste to aheavy waste removal area where the heavy waste is essentiallyautomatically removed with the wastewater stream. Thus, with the presentinvention, the heavy waste need not be manually emptied from thewastewater separator separately from the light waste, nor does the heavywaste get trapped along with the light waste. As a result, the containerdoes not need to be emptied as often. Also, the process of emptying thecontainer is less unpleasant, as there is no heavy waste decomposing anaerobically in the container and releasing noxious gases.

There may be other ways of achieving the separation of the heavy wastefrom the mixed wastewater stream through, for example, mechanical means,without departing from the scope of the invention, but such othersolutions are likely to be more complicated, more expensive and morelikely to require extra maintenance. Therefore it is believed that theuse of gravity, through relative buoyancy effects, and flow manipulationto slow the flow to maximize the potential for buoyancy separation ofthe present invention is the most preferred solution.

Referring now to FIG. 3, the quarter turn fastener 54 is shown. Thefastener 54 preferably includes a finger grip portion 56 to allow foreasy turning while opening and closing the fastener.

From its closed position, when the fastener is turned by about 90°, itis moved to its open position, and no longer grips the cover 52 to thecontainer 22.

It will be appreciated by those skilled in the art that the wastewaterseparator 10 is used in a moist environment conducive to corrosion.Thus, the wastewater separator 10 is preferably composed of moldedplastic to resist corrosion. The use of molded plastic is alsopreferable because it makes the wastewater separator 10 simpler and lessexpensive to manufacture than if metal were used. A reduction incorrosion can also be achieved through use of stainless steel, oranother metal if coated to inhibit corrosion.

While the foregoing embodiments of the present invention have been setforth in considerable detail, it will be apparent to those skilled inthe art that various modifications can be made to the invention withoutdeparting from the scope of the attached claims. Some of thesevariations are discussed above and others will be apparent to thoseskilled in the art. For example, the container 22 may be made of anysolid material sufficiently strong to contain water in the wastewaterseparator 10. Also, the preferred flow path may be any flow path whichpermits the light waste to separate from the wastewater stream in afirst direction to a collection area and permits the heavy waste toseparate from the wastewater stream in a second direction towards theheavy waste removal area 42. What is considered important in this aspectof the present invention is to provide a wastewater separator whicheffectively separates and traps light waste from a wastewater stream,while ensuring: (1) that heavy waste is not trapped in the layer oflight waste; and (2) that the heavy waste need not be emptied from thewastewater separator manually on a regular basis.

1. A method of preventing grease or oil from being carried out inwastewater from a food preparation establishment to a sewer system, saidmethod comprising the steps of: 1) entraining air into said wastewaterstream; 2) directing said wastewater stream to a separation area, aftersaid air entraining step; 3) allowing said grease or oil to rise fromsaid separation area thereby removing said grease or oil from saidwastewater stream; 4) allowing food particles to settle into saidseparation area; 5) accelerating said wastewater stream through anoutlet extending substantially to a food particle removal area, in saidseparation area, thereby sucking said food particles away from saidseparation area; and 6) directing said wastewater and said foodparticles toward said sewer system.
 2. A method of preventing grease oroil from being carried out in wastewater from a food preparationestablishment to a sewer system, said method comprising the steps of: 1)entraining air into said wastewater stream; 2) directing said wastewaterstream to a separation area of a separation area, after said airentraining step; then 3) directing said wastewater stream along apreferred flow path within said separation area, said preferred flowpath being sized and shaped to permit said grease to rise out of saidwastewater stream in a first direction to a collection area and topermit said food particles to separate from said wastewater stream in asecond direction towards a food particle removal area located in theseparation area and proximate to a floor of the separation area, whereinthe length of the flow path is maximized in the first direction; then 4)permitting said grease to rise out of said wastewater stream; 5)containing said grease within said separation area; 6) accelerating saidwastewater stream, carrying said food particles, out of said separationarea through an outlet extending substantially to the food particleremoval area, in said separation area, thereby sucking said foodparticles away from said separation area; and 7) directing saidremaining wastewater toward said sewer system.
 3. The method of claim 2,said method further comprising the steps of: providing at least onebaffle detachably attached to said container for directing saidwastewater stream along a preferred flow path within said separationarea; removing said at least one baffle from said container, cleaningaccumulated waste from said container and said baffle, and replacingsaid baffle in said container.
 4. The method of claim 2, wherein saidfirst direction of said preferred flow path extends diagonally upwardwithin said separation area.